Potential of bulk MGB2 superconductor for bulk superconductor staggered array undulator

Bulk high-temperature superconductors (HTS) have a large potential for future insertion device because of its extremely high critical current density. For example, in case for rare-earth barium-copper-oxide, its critical current density exceeds 10 kA/mm² below 10 K. This value is much higher than the equivalent current density of NdBFe permanent magnet; which is several hundred A/mm² and the engineering current density of superconducting wire of a few kA/mm². However, it is difficult to obtain large amount of bulk HTSs with same magnetic performance because of its complicated synthesis process; preparation of precursor powder, mixing, sintering, crystal growth, annealing, and precise machining. As a result, reproducibility of bulk HTS pieces is not enough for insertion device. In this work, we focused on MgB₂ bulk superconductor which has no weak-link problem and growth process is not required on synthesis. Transverse magnetic field profile for MgB₂ bulk superconductor array was estimated using a simple numerical model. Relatively small peak field variation that is lower than 1% was estimated for realistic MgB₂ bulk superconductor array. (author)